The present invention relates to an improvement in the field of testing liquids more particularly, but not by way of limitation, to a novel method and capacitance probe arrangement for determining the phase fractions of a liquid or a mobile solid.
More recently, U.S. Pat. No. 3,911,256 presented an improved apparatus for testing and analyzing a liquid. This patent provided for diverting and isolating a predetermined volummetric portion of the flow of a liquid and then measuring the differential pressure which is used to determine the density of the isolated portion. This portion was then subjected to compression of the gas fraction so that the volume of gas could be mathematically determined. Other measurements were made of the test portion so that the volume of gas and proportions of each liquid in the sample could be determined by mathematical comparative calculations.
U.S. Pat. No. 4,852,395 discloses a three phase fluid flow measuring system for measuring the volummetric fractions of gas, water and oil which included a centrifugal separator for conducting primary separation of gas from the liquid phase. A sample of the resultant fluid stream was conducted to a test chamber where it was subjected to compression of the gas fraction so that the volume of gas could be mathematically determined. The transmissivity of microwave energy through a section of the flowing stream was then measured as a way of determining the volummetric fraction of water and oil in the liquid phase.
It is also known in the art to meter aggregate flow rate and to segregate a test sample of a well stream and to record the temperature, pressure, and weight of such sample and to also determine the aggregate capacitance of the sample. The net oil, gas, and water content are then determined mathematically, after corrections for temperature.
However, all known prior art systems and methods are subject to a number of shortcomings. Some systems will not provide accurate liquid flow data if over a 5% gas fraction exists in the sample or if the fluids do not separate into their fractions by the force of gravity within a short time period. Also, inaccurate data is obtained as the degree of emulsion of different fluids increases or varies.
These problems include temperature dependance. The capacitance readings vary with sample temperature changes, which the computer must attempt to correct. However, results have been inconsistent between different sample chambers and different coatings on the capacitance probe. As the test chamber or test probes are fouled, test readings begin to vary unacceptably with the computer indicating a lower water fraction than really exists. Great difficulties have been experienced in calibrating capacitance probes which require a cumbersome and difficult procedure. Also, recalibration of current systems must be made in the event that the capacitance of the fluids change over time, or with the addition of chemicals into the fluids. However, the biggest problem remains with emulsions that remain after the time permitted for separation of the fractions and the inconsistencies in capacitance readings that result in indicating a much larger content of a fluid than is actually present. Ultimately, the only way the prior art has found to deal reliably with emulsions is to wait for the sample to separate out completely, which time period may take any where from minutes to weeks, if at all.
While the prior patents and prior art commercial probe devices have been successful to a certain extent, it is nonetheless clear that substantial room exists for affecting an advance in the art which overcomes these shortcomings in a practical and efficient manner.
It is a general object of the invention to provide an improved method and capacitance probe arrangement for testing and analyzing a fluid contained in a tank or chamber to determine the volumetric fractions of the fluids having varying permittivity contained in the tank and which overcomes the shortcomings that are found in the methods and apparatus of the known prior art.
Another object of the invention is to provide an improved method and automated system for determining the phase fractions of an oil well stream wherein the gas, water, and oil fractions of a test sample of the well stream are not separated nor need to be separated in the process of analyzing and calculating the new oil content.
Yet another object of the invention is to provide a method and capacitance probe arrangement which may accurately test and analyze test well samples which have gas fractions from 0 to approximately 100% of the total well production volume.
Another object of the invention is to provide an improved method and capacitance probe arrangement for analyzing a contained liquid having oil as a constituent which will reduce or substantially minimize the effects of any accumulated oil coating on the interior of the test chamber.
It is a further object of the invention to provide a method of analyzing a test sample of a production well stream which will provide additional data beyond the phase fractions of gas, oil and water and which will minimize the dependency on entry of accurate data relating to the densities of oil, gas and water, permitivity of oil, water, gas, etc. thereby providing "live" or real time oil and water density data.
Also, it is an object of the improved method to permit analysis and quantification of the degree of oil-water emulsion of the test sample of the well stream and to indicate the separation rate of the oil and gas fractions.
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.